FUNCTIONS

pixAverageIntensityProfile

pixAverageIntensityProfile()
Input: pixs (any depth; colormap OK)
fract (fraction of image width or height to be used)
dir (averaging direction: L_HORIZONTAL_LINE or L_VERTICAL_LINE)
first, last (span of rows or columns to measure)
factor1 (sampling along fast scan direction; >= 1)
factor2 (sampling along slow scan direction; >= 1)
Return: na (of reversal profile), or null on error.
Notes:
(1) If d != 1 bpp, colormaps are removed and the result
is converted to 8 bpp.
(2) If @dir == L_HORIZONTAL_LINE, the intensity is averaged
along each horizontal raster line (sampled by @factor1),
and the profile is the array of these averages in the
vertical direction between @first and @last raster lines,
and sampled by @factor2.
(3) If @dir == L_VERTICAL_LINE, the intensity is averaged
along each vertical line (sampled by @factor1),
and the profile is the array of these averages in the
horizontal direction between @first and @last columns,
and sampled by @factor2.
(4) The averages are measured over the central @fract of the image.
Use @fract == 1.0 to average across the entire width or height.

pixAverageOnLine

pixAverageOnLine()
Input: pixs (1 bpp or 8 bpp; no colormap)
x1, y1 (starting pt for line)
x2, y2 (end pt for line)
factor (sampling; >= 1)
Return: average of pixel values along line, or null on error.
Notes:
(1) The line must be either horizontal or vertical, so either
y1 == y2 (horizontal) or x1 == x2 (vertical).
(2) If horizontal, x1 must be <= x2.
If vertical, y1 must be <= y2.
characterize the intensity smoothness along a line.
(3) Input end points are clipped to the pix.

pixClipBoxToEdges

pixClipBoxToEdges()
Input: pixs (1 bpp)
boxs (<optional> ; use full image if null)
lowthresh (threshold to choose clipping location)
highthresh (threshold required to find an edge)
maxwidth (max allowed width between low and high thresh locs)
factor (sampling factor along pixel counting direction)
&pixd (<optional return> clipped pix returned)
&boxd (<optional return> bounding box)
Return: 0 if OK; 1 on error or if a fg edge is not found from
all four sides.
Notes:
(1) At least one of {&pixd, &boxd} must be specified.
(2) If there are no fg pixels, the returned ptrs are null.
(3) This function attempts to locate rectangular "image" regions
of high-density fg pixels, that have well-defined edges
on the four sides.
(4) Edges are searched for on each side, iterating in order
from left, right, top and bottom. As each new edge is
found, the search box is resized to use that location.
Once an edge is found, it is held. If no more edges
are found in one iteration, the search fails.
(5) See pixScanForEdge() for usage of the thresholds and @maxwidth.
(6) The thresholds must be at least 1, and the low threshold
cannot be larger than the high threshold.
(7) If the low and high thresholds are both 1, this is equivalent
to pixClipBoxToForeground().

pixClipBoxToForeground

pixClipBoxToForeground()
Input: pixs (1 bpp)
boxs (<optional> ; use full image if null)
&pixd (<optional return> clipped pix returned)
&boxd (<optional return> bounding box)
Return: 0 if OK; 1 on error or if there are no fg pixels
Notes:
(1) At least one of {&pixd, &boxd} must be specified.
(2) If there are no fg pixels, the returned ptrs are null.
(3) Do not use &pixs for the 3rd arg or &boxs for the 4th arg;
this will leak memory.

pixClipMasked

pixClipMasked()
Input: pixs (1, 2, 4, 8, 16, 32 bpp; colormap ok)
pixm (clipping mask, 1 bpp)
x, y (origin of clipping mask relative to pixs)
outval (val to use for pixels that are outside the mask)
Return: pixd, (clipped pix) or null on error or if pixm doesn't
intersect pixs
Notes:
(1) If pixs has a colormap, it is preserved in pixd.
(2) The depth of pixd is the same as that of pixs.
(3) If the depth of pixs is 1, use @outval = 0 for white background
and 1 for black; otherwise, use the max value for white
and 0 for black. If pixs has a colormap, the max value for
@outval is 0xffffffff; otherwise, it is 2^d - 1.
(4) When using 1 bpp pixs, this is a simple clip and
blend operation. For example, if both pix1 and pix2 are
black text on white background, and you want to OR the
fg on the two images, let pixm be the inverse of pix2.
Then the operation takes all of pix1 that's in the bg of
pix2, and for the remainder (which are the pixels
corresponding to the fg of the pix2), paint them black
(1) in pix1. The function call looks like
pixClipMasked(pix2, pixInvert(pix1, pix1), x, y, 1);

pixClipRectangle

PIX * pixClipRectangle ( PIX *pixs, BOX *box, BOX **pboxc )

pixClipRectangle()
Input: pixs
box (requested clipping region; const)
&boxc (<optional return> actual box of clipped region)
Return: clipped pix, or null on error or if rectangle
doesn't intersect pixs
Notes:
This should be simple, but there are choices to be made.
The box is defined relative to the pix coordinates. However,
if the box is not contained within the pix, we have two choices:
(1) clip the box to the pix
(2) make a new pix equal to the full box dimensions,
but let rasterop do the clipping and positioning
of the src with respect to the dest
Choice (2) immediately brings up the problem of what pixel values
to use that were not taken from the src. For example, on a grayscale
image, do you want the pixels not taken from the src to be black
or white or something else? To implement choice 2, one needs to
specify the color of these extra pixels.
So we adopt (1), and clip the box first, if necessary,
before making the dest pix and doing the rasterop. But there
is another issue to consider. If you want to paste the
clipped pix back into pixs, it must be properly aligned, and
it is necessary to use the clipped box for alignment.
Accordingly, this function has a third (optional) argument, which is
the input box clipped to the src pix.

pixClipRectangles

PIXA * pixClipRectangles ( PIX *pixs, BOXA *boxa )

pixClipRectangles()
Input: pixs
boxa (requested clipping regions)
Return: pixa (consisting of requested regions), or null on error
Notes:
(1) The returned pixa includes the actual regions clipped out from
the input pixs.

pixClipToForeground

l_int32 pixClipToForeground ( PIX *pixs, PIX **ppixd, BOX **pbox )

pixClipToForeground()
Input: pixs (1 bpp)
&pixd (<optional return> clipped pix returned)
&box (<optional return> bounding box)
Return: 0 if OK; 1 on error or if there are no fg pixels
Notes:
(1) At least one of {&pixd, &box} must be specified.
(2) If there are no fg pixels, the returned ptrs are null.

pixConformsToRectangle

pixConformsToRectangle()
Input: pixs (1 bpp)
box (<optional> if null, use the entire pixs)
dist (max distance allowed between bounding box and nearest
foreground pixel within it)
&conforms (<return> 0 (false) if not conforming;
1 (true) if conforming)
Return: 0 if OK, 1 on error
Notes:
(1) There are several ways to test if a connected component has
an essentially rectangular boundary, such as:
a. Fraction of fill into the bounding box
b. Max-min distance of fg pixel from periphery of bounding box
c. Max depth of bg intrusions into component within bounding box
The weakness of (a) is that it is highly sensitive to holes
within the c.c. The weakness of (b) is that it can have
arbitrarily large intrusions into the c.c. Method (c) tests
the integrity of the outer boundary of the c.c., with respect
to the enclosing bounding box, so we use it.
(2) This tests if the connected component within the box conforms
to the box at all points on the periphery within @dist.
Inside, at a distance from the box boundary that is greater
than @dist, we don't care about the pixels in the c.c.
(3) We can think of the conforming condition as follows:
No pixel inside a distance @dist from the boundary
can connect to the boundary through a path through the bg.
To implement this, we need to do a flood fill. We can go
either from inside toward the boundary, or the other direction.
It's easiest to fill from the boundary, and then verify that
there are no filled pixels farther than @dist from the boundary.

pixCropToMatch

pixCropToMatch()
Input: pixs1 (any depth, colormap OK)
pixs2 (any depth, colormap OK)
&pixd1 (<return> may be a clone)
&pixd2 (<return> may be a clone)
Return: 0 if OK, 1 on error
Notes:
(1) This resizes pixs1 and/or pixs2 by cropping at the right
and bottom, so that they're the same size.
(2) If a pix doesn't need to be cropped, a clone is returned.
(3) Note: the images are implicitly aligned to the UL corner.

pixCropToSize

PIX * pixCropToSize ( PIX *pixs, l_int32 w, l_int32 h )

pixCropToSize()
Input: pixs (any depth, colormap OK)
w, h (max dimensions of cropped image)
Return: pixd (cropped if necessary) or null on error.
Notes:
(1) If either w or h is smaller than the corresponding dimension
of pixs, this returns a cropped image; otherwise it returns
a clone of pixs.

pixExtractOnLine

pixExtractOnLine()
Input: pixs (1 bpp or 8 bpp; no colormap)
x1, y1 (one end point for line)
x2, y2 (another end pt for line)
factor (sampling; >= 1)
Return: na (of pixel values along line), or null on error.
Notes:
(1) Input end points are clipped to the pix.
(2) If the line is either horizontal, or closer to horizontal
than to vertical, the points will be extracted from left
to right in the pix. Likewise, if the line is vertical,
or closer to vertical than to horizontal, the points will
be extracted from top to bottom.
(3) Can be used with numaCountReverals(), for example, to
characterize the intensity smoothness along a line.

pixFindAreaFraction

pixFindAreaFraction()
Input: pixs (1 bpp)
tab (<optional> pixel sum table, can be NULL)
&fract (<return> fg area/size ratio)
Return: 0 if OK, 1 on error
Notes:
(1) This finds the ratio of the number of fg pixels to the
size of the pix (w * h). It is typically used for a
single connected component.

pixFindAreaFractionMasked

pixFindAreaFractionMasked()
Input: pixs (1 bpp, typically a single component)
box (<optional> for pixs relative to pixm)
pixm (1 bpp mask, typically over the entire image from
which the component pixs was extracted)
tab (<optional> pixel sum table, can be NULL)
&fract (<return> fg area/size ratio)
Return: 0 if OK, 1 on error
Notes:
(1) This finds the ratio of the number of masked fg pixels
in pixs to the total number of fg pixels in pixs.
It is typically used for a single connected component.
If there are no fg pixels, this returns a ratio of 0.0.
(2) The box gives the location of the pix relative to that
of the UL corner of the mask. Therefore, the rasterop
is performed with the pix translated to its location
(x, y) in the mask before ANDing.
If box == NULL, the UL corners of pixs and pixm are aligned.

pixFindAreaPerimRatio

pixFindAreaPerimRatio()
Input: pixs (1 bpp)
tab (<optional> pixel sum table, can be NULL)
&fract (<return> area/perimeter ratio)
Return: 0 if OK, 1 on error
Notes:
(1) The area is the number of fg pixels that are not on the
boundary (i.e., are not 8-connected to a bg pixel), and the
perimeter is the number of fg boundary pixels. Returns
0.0 if there are no fg pixels.
(2) This function is retained because clients are using it.

pixFindPerimSizeRatio

pixFindPerimSizeRatio()
Input: pixs (1 bpp)
tab (<optional> pixel sum table, can be NULL)
&ratio (<return> perimeter/size ratio)
Return: 0 if OK, 1 on error
Notes:
(1) We take the 'size' as twice the sum of the width and
height of pixs, and the perimeter is the number of fg
boundary pixels. We use the fg pixels of the boundary
because the pix may be clipped to the boundary, so an
erosion is required to count all boundary pixels.
(2) This has a large value for dendritic, fractal-like components
with highly irregular boundaries.
(3) This is typically used for a single connected component.
It has a value of about 1.0 for rectangular components with
relatively smooth boundaries.

pixFindPerimToAreaRatio

pixFindPerimToAreaRatio()
Input: pixs (1 bpp)
tab (<optional> pixel sum table, can be NULL)
&fract (<return> perimeter/area ratio)
Return: 0 if OK, 1 on error
Notes:
(1) The perimeter is the number of fg boundary pixels, and the
area is the number of fg pixels. This returns 0.0 if
there are no fg pixels.
(2) Unlike pixFindAreaPerimRatio(), this uses the full set of
fg pixels for the area, and the ratio is taken in the opposite
order.
(3) This is typically used for a single connected component.
This always has a value <= 1.0, and if the average distance
of a fg pixel from the nearest bg pixel is d, this has
a value ~1/d.

pixFindRectangleComps

pixFindRectangleComps()
Input: pixs (1 bpp)
dist (max distance allowed between bounding box and nearest
foreground pixel within it)
minw, minh (minimum size in each direction as a requirement
for a conforming rectangle)
Return: boxa (of components that conform), or null on error
Notes:
(1) This applies the function pixConformsToRectangle() to
each 8-c.c. in pixs, and returns a boxa containing the
regions of all components that are conforming.
(2) Conforming components must satisfy both the size constraint
given by @minsize and the slop in conforming to a rectangle
determined by @dist.

pixMinMaxNearLine

pixMinMaxNearLine()
Input: pixs (8 bpp; no colormap)
x1, y1 (starting pt for line)
x2, y2 (end pt for line)
dist (distance to search from line in each direction)
direction (L_SCAN_NEGATIVE, L_SCAN_POSITIVE, L_SCAN_BOTH)
&namin (<optional return> minimum values)
&namax (<optional return> maximum values)
&minave (<optional return> average of minimum values)
&maxave (<optional return> average of maximum values)
Return: 0 if OK; 1 on error or if there are no sampled points
within the image.
Notes:
(1) If the line is more horizontal than vertical, the values
are computed for [x1, x2], and the pixels are taken
below and/or above the local y-value. Otherwise, the
values are computed for [y1, y2] and the pixels are taken
to the left and/or right of the local x value.
(2) @direction specifies which side (or both sides) of the
line are scanned for min and max values.
(3) There are two ways to tell if the returned values of min
and max averages are valid: the returned values cannot be
negative and the function must return 0.
(4) All accessed pixels are clipped to the pix.

pixRankColumnTransform

PIX * pixRankColumnTransform ( PIX *pixs )

pixRankColumnTransform()
Input: pixs (8 bpp; no colormap)
Return: pixd (with pixels sorted in each column, from
min to max value)
Notes:
(1) The time is O(n) in the number of pixels and runs about
50 Mpixels/sec on a 3 GHz machine.

pixRankRowTransform

PIX * pixRankRowTransform ( PIX *pixs )

pixRankRowTransform()
Input: pixs (8 bpp; no colormap)
Return: pixd (with pixels sorted in each row, from
min to max value)
Notes:
(1) The time is O(n) in the number of pixels and runs about
100 Mpixels/sec on a 3 GHz machine.

pixResizeToMatch

PIX * pixResizeToMatch ( PIX *pixs, PIX *pixt, l_int32 w, l_int32 h )

pixResizeToMatch()
Input: pixs (1, 2, 4, 8, 16, 32 bpp; colormap ok)
pixt (can be null; we use only the size)
w, h (ignored if pixt is defined)
Return: pixd (resized to match) or null on error
Notes:
(1) This resizes pixs to make pixd, without scaling, by either
cropping or extending separately in both width and height.
Extension is done by replicating the last row or column.
This is useful in a situation where, due to scaling
operations, two images that are expected to be the
same size can differ slightly in each dimension.
(2) You can use either an existing pixt or specify
both @w and @h. If pixt is defined, the values
in @w and @h are ignored.
(3) If pixt is larger than pixs (or if w and/or d is larger
than the dimension of pixs, replicate the outer row and
column of pixels in pixs into pixd.

pixReversalProfile

pixReversalProfile()
Input: pixs (any depth; colormap OK)
fract (fraction of image width or height to be used)
dir (profile direction: L_HORIZONTAL_LINE or L_VERTICAL_LINE)
first, last (span of rows or columns to measure)
minreversal (minimum change in intensity to trigger a reversal)
factor1 (sampling along raster line (fast scan); >= 1)
factor2 (sampling of raster lines (slow scan); >= 1)
Return: na (of reversal profile), or null on error.
Notes:
(1) If d != 1 bpp, colormaps are removed and the result
is converted to 8 bpp.
(2) If @dir == L_HORIZONTAL_LINE, the the reversals are counted
along each horizontal raster line (sampled by @factor1),
and the profile is the array of these sums in the
vertical direction between @first and @last raster lines,
and sampled by @factor2.
(3) If @dir == L_VERTICAL_LINE, the the reversals are counted
along each vertical column (sampled by @factor1),
and the profile is the array of these sums in the
horizontal direction between @first and @last columns,
and sampled by @factor2.
(4) For each row or column, the reversals are summed over the
central @fract of the image. Use @fract == 1.0 to sum
across the entire width (of row) or height (of column).
(5) @minreversal is the relative change in intensity that is
required to resolve peaks and valleys. A typical number for
locating text in 8 bpp might be 50. For 1 bpp, minreversal
must be 1.
(6) The reversal profile is simply the number of reversals
in a row or column, vs the row or column index.

pixScanForEdge

pixScanForEdge()
Input: pixs (1 bpp)
box (<optional> within which the search is conducted)
lowthresh (threshold to choose clipping location)
highthresh (threshold required to find an edge)
maxwidth (max allowed width between low and high thresh locs)
factor (sampling factor along pixel counting direction)
scanflag (direction of scan; e.g., L_FROM_LEFT)
&loc (location in scan direction of first black pixel)
Return: 0 if OK; 1 on error or if the edge is not found
Notes:
(1) If there are no fg pixels, the position is set to 0.
Caller must check the return value!
(2) Use @box == NULL to scan from edge of pixs
(3) As the scan progresses, the location where the sum of
pixels equals or excees @lowthresh is noted (loc). The
scan is stopped when the sum of pixels equals or exceeds
@highthresh. If the scan distance between loc and that
point does not exceed @maxwidth, an edge is found and
its position is taken to be loc. @maxwidth implicitly
sets a minimum on the required gradient of the edge.
(4) The thresholds must be at least 1, and the low threshold
cannot be larger than the high threshold.

pixScanForForeground

pixScanForForeground()
Input: pixs (1 bpp)
box (<optional> within which the search is conducted)
scanflag (direction of scan; e.g., L_FROM_LEFT)
&loc (location in scan direction of first black pixel)
Return: 0 if OK; 1 on error or if no fg pixels are found
Notes:
(1) If there are no fg pixels, the position is set to 0.
Caller must check the return value!
(2) Use @box == NULL to scan from edge of pixs

pixTestClipToForeground

l_int32 pixTestClipToForeground ( PIX *pixs, l_int32 *pcanclip )

pixTestClipToForeground()
Input: pixs (1 bpp)
&canclip (<return> 1 if fg does not extend to all four edges)
Return: 0 if OK; 1 on error
Notes:
(1) This is a lightweight test to determine if a 1 bpp image
can be further cropped without loss of fg pixels.
If it cannot, canclip is set to 0.

pixWindowedVarianceOnLine

pixWindowedVarianceOnLine()
Input: pixs (8 bpp; no colormap)
dir (L_HORIZONTAL_LINE or L_VERTICAL_LINE)
loc (location of the constant coordinate for the line)
c1, c2 (end point coordinates for the line)
size (window size; must be > 1)
&nad (<return> windowed square root of variance)
Return: 0 if OK; 1 on error
Notes:
(1) The returned variance array traverses the line starting
from the smallest coordinate, min(c1,c2).
(2) Line end points are clipped to pixs.
(3) The reference point for the variance calculation is the center of
the window. Therefore, the numa start parameter from
pixExtractOnLine() is incremented by @size/2,
to align the variance values with the pixel coordinate.
(4) The square root of the variance is the RMS deviation from the mean.

pixaFindAreaFraction

NUMA * pixaFindAreaFraction ( PIXA *pixa )

pixaFindAreaFraction()
Input: pixa (of 1 bpp pix)
Return: na (of area fractions for each pix), or null on error
Notes:
(1) This is typically used for a pixa consisting of
1 bpp connected components.

pixaFindAreaFractionMasked

pixaFindAreaFractionMasked()
Input: pixa (of 1 bpp pix)
pixm (mask image)
debug (1 for output, 0 to suppress)
Return: na (of ratio masked/total fractions for each pix),
or null on error
Notes:
(1) This is typically used for a pixa consisting of
1 bpp connected components, which has an associated
boxa giving the location of the components relative
to the mask origin.
(2) The debug flag displays in green and red the masked and
unmasked parts of the image from which pixa was derived.

pixaFindPerimSizeRatio

NUMA * pixaFindPerimSizeRatio ( PIXA *pixa )

pixaFindPerimSizeRatio()
Input: pixa (of 1 bpp pix)
Return: na (of fg perimeter/(2*(w+h)) ratio for each pix),
or null on error
Notes:
(1) This is typically used for a pixa consisting of
1 bpp connected components.
(2) This has a minimum value for a circle of pi/4; a value for
a rectangle component of approx. 1.0; and a value much larger
than 1.0 for a component with a highly irregular boundary.

As a valued partner and proud supporter of MetaCPAN, StickerYou is
happy to offer a 10% discount on all Custom Stickers,
Business Labels, Roll Labels,
Vinyl Lettering or Custom Decals. StickerYou.com
is your one-stop shop to make your business stick.
Use code METACPAN10 at checkout to apply your discount.